Śatapatha Brāhmaṇa ("of a hundred paths") 11.2.4.6

11.2.4.6

prāṇa evānnādaḥ prāṇena hīdamannamadyata udāna evānnaprada udānena hīdamannam pradīyate sa yo haitāvannādaṃ cānnapradaṃ ca darśapūrṇamāsau vedānnādo haiva bhavati pra hāsmā annādyaṃ dīyate

The out (and in)-breathing (the mouth) is the eater of food, for by means of the out (and in)-breathing this food is eaten; and the up-breathing is the giver of food, for by the up-breathing this food is given to him.